Shuttle valve



Oct. 9, 1951 A, G, wlNcHEsTER 2,570,897

v SHUTTLE VALVE Filed Aug. 2, 1944 l 4 Sheets-Sheet l @if Www@ J- J .114; V4 l l? l i ([fj", M743 E l' i: l :315 4]: l Z l 37 l l JJ I' l f- H! J6 J "l l L i J0 l z W3 E I l l E i l f i I l j l l E i; JJ y l -5 l I H' J3 j] i l l 5- ,MW/.5 (Ittorneg l Oct. 9, 1951 A, G, wlNCHESTER 2,570,897

SHUTTLE VALVE 4 Sheets-Sheet 3 Filed Aug. 2, 1944 WSNS* ma ds @if B26 iatenteci ct. 9, i951 tion ofMalfyland r signor to Gyerctor. MayV Corporation, a corpora- Applicfation August 2, 1944, Serial No. 547,790

My invention relates toa `hydraulic direction?? rectifying valve, rthat is, a Svalve which .will re.- ceive'fluid ifiowing tliereintoV from different and reversible directions, but Vwhich will discharge fthe fiuid,"inuniow manner, in a single, predetermined direction.

Anobject of my'invention is to provide an ecient and reliable valve ofthe general type descrbedffwhch is simple, compact, vhavingA .only limited volumetric requirements, and sturdy; displaying long wear; `which has only a limited number 'of' .moving vparts and yrequires 'but .minimum `attendance and supervision, and Ihence has W 'maintenance and 'operational costs, Aand Whichat .the same time vinvolves entirely reasonable rst cost.

.Otherxobjects and advantages will in .part .be obvious and in part pointed out hereinafter', in connection with 'the description of .the .construction disclosed iin the .accompanying drawings.

vMyfinvention accordingly 'consists in the sev# era'l elements, features of constructior'i andI operational parts, and in the relation of eachof the same to oneormoreof the others', all vas described herein and as is fully set forth in .the accompanying claims.

In the drawings: LE igure l is a View inside elevation of a pre.- ferred embodimentjof my invention; -`Figures ,2 @m13 respectively constituting top and bottom plans thereof and Figure 4 an end elevation,.tliis onenlarged scale Figures is a vertical longitudinalsection on enlarged scale taken on line 5 5 in -]& i,f,1fure2; while Fiaures 16. 'Lend 8 are respectively, transverse vertical sections on enlarged scale taken onilines Ee-6,31%? and 8 8 in Figure 1.

AS .conducive .to .a more thorough understandf nsofcertain features of myfinventien. it margine nete@ at this peint thatneedzhas arisen from time totimein many walks of industry for cene necting hydraulic stand-by systemenergizing equipment, which is vnormally blocked r)from Ia mainhydraulic-system, into that main hydraulic system. Now, this stand-by equipment lfre-- quently is reversible for supplying uid ineitlier direction to the main hydraulic system. The stand-by .equipmentusually is cut into kthe main V system by valve means of the shiftover -type when occasion requires. For simplicity, it is recognized as desirable to have the cutin or shirtfover Avalve last referred -tor operatefdeither bycr as an incident to energizationof` thestandby equipment, so that'the latter-will becutintc the'main system brought -to operating speed. Now, difliculty is encountered infthat-the yshiftpver valve must always operate lin a single ,direcf tionin order to, establish hydraulic circuits connecting the lstand-by equipment to the .main

,4 cnims; (c1. 137%144) especially when the stand-by equipment itself is reversible k in direction of energization. It is, therefore, necessary to employ means for-impress-- ing the positive pressure of the stand-by equipment, regardless of which end thereof is the momentary high pressure outlet, in but .a single direction on the shift-over yalve. rThe need ior such equipment, and. an adaptation of my present invention to the problem are suggested in a come panion application for lUnited States VLetters Patent, Serial No. 547,788, flied of even oateherewith, in the names of Albert Rivington Stone and Albert Girvin Winchester, now Patent 2,512,119 of June 20, 1950. .1

The -manner of .resolving these diinculties is therein siown, in schematic form, to comprise a direction-rectifying shuttle valye, .c ertain novel details of which comprise the subject metterci the present application. lt iiSLof .course readily understood that meco-.pending application, JuSt identineddiscloses only asingle one of many widely lvaried and diversiied possible applications omyinew-valveconstruction A n ,irriportant object of my inventiom therefore, is to remove or satisfythedisadvantages and dficultes referred to as encounteredintheprior art, and toprovidea hydraulic directionrrectifyins Shuttle valve v.willen is Simpleandrelable in Operation and which serves eleetively vir1 eenn QtiDf/ TeYerSbledfecion Stand-.PY ldalllc equipment with a Shiftever valve movable in buta 4single direction from its cut-outpo'sition.

A valve casing portion I0 of metalis provided, Whiehfferexample, is generally rectangular in both longitudinal Vand transverse sections. End p1ate s l2, ofthe casing close u01T the respece tive ends ef portion l0, and are Seeuredthereto in anysuitable manner, as by bolts. L3. Eloneatednelts i4 vextend through eaeneportien te f r em ti1e.ten.neartheleneitudnal Wallstnereef. .and eeatinte a cooperating bottom` easinememleer.. net. ehevvn. suehae a plate. headenerthe 111e which covers the entire bottom .ereaof the P.Qrtqngmv Q The vai-ve easing eemprisline the .Several parte iustmentiened Serves te heuseitwo substantially separate andirldependent valves. exeeptferI eertae features which are in eemmen tn .theftwo valves. fer convenience in Construction as -iviil beine-re fully developed hereinafter, teeetnerwith their attendant ports and sliding valve elements. .The Dartefef elle Saleh valve are designated by the pumeratpreilx A, w l 1ile the partsotthesec- Vond valve are vsimilarly designated by the prefix B.

Trrevde ferveueh ralves, the. easnsreltiea Il) has two adjacent long-itudinahbcres i5 :eo whiehLfeaeXamPle-have axesena eenirawertical plane through the casing. Parallel to these two bores and illustratively extending through the geometric center of casing portion II! is a third bore I6. This bore is tapped as from the right end (Figure 5) of the casing but terminates short of the left end thereof. While bores AI5 and BIE extend through end plates II, I2, the bore IIS terminates at its right end against the solid wall of end plate I2. Bores AIS-BIS are respectively dened, within' casing-I0, by sleeves A22, B22 let into the casing.

Sliding valve elements, in the form of piston valves A8, B8, and somewhat shorter than the length of the valve casing Ill, are snugly received for limited longitudinal movement in corresponding bores AI 5, BIS.V Thevalve elements comprise reduced sections A9,H A-IILAII and B9, BIB, BII defined between larger diameter end portions AI 2, AI3, and BI2,BI3, and by similarintermediate portions AI4, A-I 5 and BIG, BIS, also of larger diameter.

Each valve element A8, B3 it-will be understood is of the balanced, spool type. End plates II, I2 permit ready installation of the spool-type piston valves,as well as providing ready access to the interior of the valve for repairs or overhauling, when occasion requires. Fluid inlets, more particularly described hereinafter, are provided at the several ends of these valve elements and are connected as to stand-by hydraulic equipment with which the. valve is intended to cooperate. When the stand-by equipment is idle, the pressure exerted inV each of the hydraulic `lines by the stand-by equipment will be the same, and the valve elements are designed to stand in a neutral, centered position. When this condition is maintained, the relation of the valve ports, later to be described, and the sections of the valve elements is such that these ports are closed, and no flow occurs through the valve. K

The valve elements are centered during their rest or inactive condition-their state of hydrostatic balance--by spring-urged followers, disposed one at each end of each valve element. Since the construction, dimensions and characteristics of the follower assembly is the same in each instance, the description of a single construction will suiiice. I shall choose, for convenience, the assembly at the right (Figure 5) of the A piston. End section AIS is recessed at AI'I. Follower AIS, disc-like in contour and of diameter sufcient to seat against the end face of section AI3,

is sldably tted on bolt AIS, which terminates at inner end in an enlarged cylindrical head A20. End plate I2 is internally threaded at A4I along bore AIS to receive the corresponding threads of shank A42 of enlarged nut A43, to Which nut the bolt AIS is made fast as by threaded iit A3I. A coiled spring A44 disposed about bolt AIB extends between follower AIB and bearing surface A45 fast to and forming part of nut A43, and serves, in conjunction with the spring of like characteristics at the other end of bore AIS, to keep the valve element A8 normally in mechanical balance. The same construction is provided, and the same conditions maintain, at the other end of valve element AIS and at both ends of valve element BI5.

For convenience, I will now discuss the construction, and with it the operation, of the B valve, shown at the bottom in Figures 4 through 8, inclusive. With it will be described certain features of construction which are in common to both the A and B Valves.

In the aforementioned co-pending application,

4 the B valve is adapted to control connection of a hand-driven stand-by hydraulic pump to a main hydraulic system through shift-over valve means. While the hand pump is designed to be energized in either direction of rotation, the shift-over valve must be moved in but a single direction, all as has been suggested hereinbefore. Valve B serves admirably to fulll these requirements.`

To this end, the -valve is provided with end ports B4 and B1 which serve to control the valve piston B8. Port B4 is disposed at the right end of casing portion 4II) (Figure 5) at the end of bore BIS, while port B1 is disposed at the-left end thereof, also at theend of bore BIE. Bore BI leads directly and tangentially from the bottom of casing portion IU to a corresponding portV indicated by the same reference numeral BI.

The relation of port BI and bore BI is best shown in Figure 8. This port BI has generally the shape of an annulus in the longitudinal sleeve B22 (see also Figure 5) let4 into casing. rlhe continuity of the sleeve is maintained, leaving port BI substantially continuous and uninterrupted, by linking web portions B23,v B24, B25 (Figure 8) which extendacross the width of the annulus. Since the mechanical construction of all the ports arranged along the extent of the bores BI5 and AIE are substantially the same, the details of the construction of the other ports, for simplicity, will in large measure be omitted, except. for certain details which are unique to the particular port. f

Referring now t0 Figure 5, it will be seen that bore BI near its lower end, is connected by a longitudinal passage B26, disposed near the bottom of casing portion II), and extending to the right therein, to a bore B4 leading vertically near the right end of the casing to port B4 and the end of piston B8.

It will be observed that in the present embodiment, I provide port BI on the left (Figure 5) of the transverse center line of casing Il). Symmetrically therewith, I provide a bore B3 leading to port B3, on the opposite or right side of the transverse center line. ThisA construction is shown in Figures 3, 5 and 6. Bore B3 lets tangentially into port B3. In turn, port B3 lets into main bore BIB.

Ports BI and B3 constitute the pressure ports for connecting the valve with a suitable pressure source. In the case of my co-pending application already referred to, this is the hand-driven stand-by pump. At any particular moment during operation, one said port will be at high pressure and the other at low pressure, depending upon the direction of rotation of the pump. The pressures of the ports will be reversed upon reversal of direction of rotation of the pump.

In manner similar to that described with reference to bores BI and B4, bore B3 is connected, for reasons which will( be developed hereinafter, to port B1, disposed at the left end of bore BIE, as seen in Figure v5.v To this end, passage B29 (Figures 6 and 8) extendsfrom bore B3 to the left, near the bottom of the casing to port B1. Passage B29 is not fully disclosed in the drawings, because of the direction in which the sectional views are taken; however, it is substantially the same as the construction heretofore described with respect to ports BI and B4.

Centrally of bore BIS is port B2 (Figure 5), to which extends bore B2 from the bottom exterior (Figures 3, 5 and 7). This serves as an outlet passage. i

o 5 V*I'Ports B5 and B6 l'flank ports BfVandl BI,`r'e' spectively, on the rightandleft'hand sides(Fig-. ure and let into bore'BiS. Bothports B5 and Blv 'are in communicationwith central' bore I6 (Figure 5). Thisbore'is in fturn let into transverse central bore '21`(Figuresf5 'and 7) which illustratively leads toa suitable disposal reservoir for excess andexhaust liquid. This reservoir takestheform lof an expansion'tank in the copending application.

In'Figure 5 the solid line construction depicts rest position of the valve. Thev pressure on opposite ends of valve element. B isthe same. The valveelement is in hydrostatic balance, andthe pressuresource, feeding in throughl ports Bi and B3,\is at rest. In this condition 'ofV the valve, pressure portsBi, B3 are blocked vby enlarged portions B l d, 'B I 6- of thevalve element. Both outlet port'B2 and exhaustfports- B5, B6 are sealed against the pressure ports'a'nd against the endports by the interposition of these enlarged portions Blf'i, B56 of the Valve element. Rest conditions maintain.

Let us' now assume, however, that pressure is appliedV across ports BUB?)v from any suitable external source; as for example, from the handdriven lpurnp of the (io-pending application. Let us Vfurther assume that 'it is the port Bi which is at high pressure, port B3 being at low pressure.

Withv this understanding, uid 'under positive pressure will enter borev B'I. 'At passage B26, part of the nuid under pressure 'will course to the right in Figure 5, te the port Bil. There it islet into bore Bi5 at the'right fend of sliding valve element B8. Impinging'against'end plate BIS, and the end piston B8, it forces the piston to the left in Figure 5, withv the aid of the coil spring at the right end, and against the compression force of the coilfspringvat the left end. Longitudinal movement is continueduntil a position of' equilibrium is reached. Enlargedportion Bis moves to block'p'ortBG. Reduced section portion B16 Visnow"`rnoved` to a position whereby high pressure port BI opens directly into what properlymay be termed the unifiow outlet port'B2.

Fluid` at Ythe left end of piston B8 meanwhile is discharged as throughport B1 and (see Fig. (i) through bores lB29 rand' B3 which n connect the discharge with the pump intake. Y Without suitable ventingof the piston discharge, either the Original condition of hydrostatic balance would remain substantially undisturbed, or if sucient pressure were impressed on the right end of' the valve to bring about a condition of incipient movement, damage or even rupture of the valve might quite likely occur. Y Alsofjwhen valve piston B8 moves to the left, asseen in Figure 5, reduced section portion Bil uncovers Vports B3 and B5, throwing B3 into connection with B5. A connection of the low pressure side of the pressure source, such as the pump,l thus is established through bore B3, across ports B3 and B5 in' bore-BI 5, and through bores I6, I1 and 28 ('see Figure 7), respectively, with a'V storage tank, bleeder fluidreservoir, or the like. In the co-pending application thisV connection ensures an adequate supply of fluid on the pumpv intake and avoids thev pumping of air.

LetV us now assume that the direction of energization of the pressure source, for example, the hand-driven pump in the co-pending application. is reversed in direction'of rotation. B3 is now the high pressure 'side,'while BI/ is the low pressure side.

i From borey B3 through I'p'assageBZ9. (Figure 6) 6 tiielpressure-uid courses 5to therleftin- Figure:5 to! port B1. lrEntering boreBI 5y at 'port.B1, ...this fluid forces the sliding piston valve B8 vtothe right, withthe aid of the left-"hand-.coil spring, and against the compression stresses in Vspring B24. Piston valve B8Lis movedto the right,fFig ure 5, from its neutral or-rest position.' PortsB-3'. and B2 are thrown into communication with each other, by reduced'section valve portionBl D, and pressure -uid from highpressureport B3. courses directly to unirlow outlet port B2,and thence through outlet bore B2 to a suitableiload, suchas the shift-over valve described in the c opending application. It is to be noted vthata rectifying action takes place, in that luniow. discharge occursthrough outletport B2, regardless of the direction in which pressure is appliedon pressure ports Bi,B3. The direction of'ow through B2 is the same, no matter whether it is Blfor B3 which is at high pressure. At the same time, fluid atthe rightv end ofl bore BIE, is expelled throughBl, passage B26, and thence to bore Bl. Ports BI. andB. are open to .each other, and thus the low pressure bore BI isconnected through the ports with conduit I6. AAs already mentioned (see Fig. 7) conduit i6 illus.,- tratively is connected with a fluid reservoirvby the respective bores 21 and 28.

Fluid as from the low pressure side-of the unirdirectional load energized from B2 returns through passage 3i! (Figures 3 and 7) communicating with the forward (left end in Figure '7) end of passage 21. The return uid from the load thus courses to the junction of-,passages 21 and 28, and the greater part thereof returns through the bottom end of passage 28 to the low-pressure side of the power source, such las the hand-driven pump, not shown, although-any excess will pass upwardly, to the expansiontank,` also not shown.

Up to this point, the detailed discussion has dwelt entirely with the BV sectiony of the tdual valve. We will now consider, in its turn, the A part of the valve giving particular-attention to certain preferred structural details. Here use is made, for the discharge of the direction-rectified pressure fluid, of the same outlet vport B2 as was used for the B valve. Similarly, use is made in common with the B valve, of the bore I6, passage 21, passage 28 and passage 30.

For convenience in design, one pressure lead through the plate or header (not shown) is provided at'3l (see Figure 3 near the left side). By means of a conduit formed by groove 32 illustratively in the bottom surface 33 ofcasing portion IE! and in the cooperating top surface ofthe header, not shown, the fluid isy conductedrfrom 3| to the right and upwardly in Figure 3, to the passage 35 (Figures 3 and 8). Passage 3d (Fig-. ure 8) communicates at its upperV end with a lateral bore 35 leadingY tangentially to port A3 which is disposed in bore Ai5, on the left of the transverse center line in Figure 5. Passage 36` (Figures-6, '1 and 8) extends from A3 to 'port A1 disposed at theiright end of bore A-l 5 in Figure 5 and communicating with the corresponding `end of piston A8. This passage is disposed substantially parallel with andiin front of the plane-'of the paper in Figure 5.

Similarly, pressure lead 31 extends fromthe other leadv of pressure source from the-header (not shown) through grooveV 38 in casingrbottom 33 to vertical passage 39 (Figures Stande). Passage 39'connects at'itsupper-end with-lateral bore 40;' which "lets; Atangentially linto--port .-A-l

Port-'AI opens into bore AI5 on the right side of the transverse center line in Fgure. Passage 4i extends from passage 4I) adjacent port AI, to port A4 at the left end (Figure 5) of bore AI5.

A port A2 is provided, disposed between pressure ports Ai, A3 in Figure 5, and along the transverse center line therein. This uniow outlet port A2 by-passes and is sealed from outlet passages i6 and 21. It connects with and empties through port B2, near the bottom of the latter.

Exhaust ports A5 and A6 are provided, symmetrically flanking, in Figure 5, the respective pressure ports A3 and AI. They are normally sealed from these latter ports when the piston valve is in its hydrostatically balanced or rest position. At all times these ports A5 and AG, in common with similar exhaust ports B5, B6 of the B valve, are in communication with bores or passages I5, 21, 28 and 35 which they shareI in common with the B valve components.

Normally, and just as is the case with the B valve, when the piston A is centered in hydrostatic balance, the pressure ports Al, A3 are sealed from uniflow outlet port A2. No fluid courses the system, and the system controlled by the valve is at rest. It is desired to ensure that regardless of the direction in which energization of the pressure system occurs, flow through the outlet port A2 will always be in the same direction.

To illustrate how this objective is achieved, assume that the source of pressure, such as the motor-driven pump in the copending application, is energized in such direction that port A3 is the high pressure port. In that case pressure fluid will enter at 3| in Figure 3, will course groove 32 to vertical passage 34 (Figure 8) to traverse passage 35, and thence tangentially into port A3. Simultaneously, part of this fluid will course from horizontal passage 35 through longitudinal passage 33 to the rightin Figure 5 to the end port A1 at the right end of bore Ai5. With the aid of coil spring A45 and against the compression stress of the coil spring at the left end of the bore Al5, this pressure fluid moves the piston A8 to the left in Figure 5. Port A3 is placed in communication, through reduced section portion Al@ of piston A8, with outlet port A2, and discharges directly thereinto. This fluid courses down bore A2, sealed from and by-passing conduits IE and 21, and communicating with outlet bore B2. Thence it passes to a suitable load. This, for example, may be the shift-over valve of the c opending application, which must always be moved in but a single direction, regardless of the direction in which it is energized.

Fluid meanwhile is forced from the left end of bore Al 5, through port All and thence through passages 4| and lil) to port Ai. By reduced section portion Ai i, port Al is brought into communication with port AE. Any excess iluid is dicharged from Al, through A6 into passage I5 while the rest returns to the pump through conduits 5G, 39, 38 and 31.

Should now, the direction of rotation of the energizing source, such as the motor-driven pump, be reversed from that just described, the direction of operation is just reversed. Al will now be the high pressure port; A3 the low pressure port.

Fluid will enter from the bottom header, not shown, under pressure at 31 in Figure 3.

8 l, Through groove 38git passes Vto vertical passage 3S (Figure 6), and` thence, at the upper end of passage 38, through lateral bore 4G. The fluid enters tangentially into port AI. At rst this Vvalve is inv hydrostatic balance, and port AI is A2 connects directly with the unidirectional load.

It will be seen that the eiect of the valve A is to rectify the direction of flow of the pressure fluid, and to discharge the same in but a single direction of flow, regardless of the direction in which the source of pressure is energized.

Fluid forced from the right end of bore Al5, as a result of movement of piston A8 to the right in Figure 5, escapes through port A1, through passage 36 to transverse passage 35 and thence to port A3. Reduced section portion A9 of piston A8 interconnects low pressure port A3 with exhaust port A5. This latter port in turn exhausts through bore i6 (left end in Figure 5) through transverse passage 21 (Figure 7) to vertical passage 28, which, as previously noted is connected with a storage tank or reservoir.

Through passage 30 (Figures 5 and 7) extending vertically from bottom face 33 of casing portion i6, return fluid from the pressure load, such as the shift-over valve, passes up to transverse bore 21 at the left in Figure 7, across this bore 21 to the right, and thence to vertical passage 28. Where bore I5 lets into bore 21, this exhaust fluid from the load mingles with the exhaust uid from A5 or AS. 21 and 28 (Figure '1), the exhaust fluid branches. The greater part courses down leg 28 and thence to the return side of the pressure energy source, such as the motor-driven pump. The excess fluid courses up leg 23, and thence to a suitable storage reservoir, such as an expansion tank. Later, as the system requires it, iiuid will be fed back as by gravity from the reservoir.

At times I find it advantageous to design the cooperating base plate or header so that both A and B valves are operated simultaneously in the same effective direction from the same pressure source. In such case, to illustrate, high pressure fluid may Venter, for example, at both A3 and B3 at the same time, coursing to A1 and B1. respectively, and moving A piston to the left and B piston'to the right in Figure 5. Then A3 connects with A2 and B3 with B2, both passing uid to bore B2, Exhaust-fluid courses from A4 to Al, and from B4 to Bl, and thence to A6 and B6, respectively. From I6 the iluid courses to 21 and thence to 28, in manner already described. The larger volume of fluid thus handled effectively precludes danger of pumping air from or to the expansion tank which may be placed on the exhaust side of the system controlled by this valve.

It is to be noted that immediately upon removal ofY a condition of hydraulic unbalance from the system, as upon deenergization of the energizing pump' or pumps, the springs at each end of the piston valve elements will restore these elements to their rest position, corresponding to hydrostatic balance. In these positions the valve At the junction of bores elements block the pressure ports AI, A3 and BI, B3, and isolate uniiiow outlet ports A2, B2 and exhaust ports A5, A6, B5 and B6, respectively. I have found that by constructing piston valves of the spool type, which have quick opening and closing characteristics, I achieve the advantages that both pressure ports are blocked simultaneously, and at the same time, detrimenta1 wire drawing is substantially eliminated.

Connecting ports A5, kA6, B5, B6 to common -passages or bores inside casing I0 contributes appreciably to the simplicity, economy and eiiiciency of design, and permits making the valve compact and rugged in construction. Simplicity of design, ruggedness of construction, and diminished rst cost are also contributed to by channeling outlet port A2 into bore B2. By mounting the valves A and B in the single casing, each with its attendant complement of piston valve elements, ports, etc., important economies in size, constructional costs, etc., are obtained, without detracting in any Way from overall eiliciency, ease of access for overhauling and repairs, and the like.

The low pressure side of the line is always connected to a suitable return circuit, in closed connection, regardless of the direction of ow of the pressure source. The storage reservoir, such as an expansion tank, with which my new valve may be associated, serves effectively to remove temporarily excess fluid from the system and to restore it automatically as and when, and in the amounts, required.

The A and B valves can be operated separately, alternatively and independently of each other, as when each is handling a comparatively light load; or they can be operated simultaneously and mechanically and hydraulically in parallel, for comparatively heavy loads.

Flow rectification is provided, with discharge through unifloW outlet, in simple and eflicacious manner.

I claim:

l. As a new article of manufacture, a hydraulic direction-rectifying Valve, comprising a multiported, longitudinally-bored valve casing, and including pressure ports for connection across a reversible-direction source of pressure uid for selectively leading in the pressure fluid, a uniiiow high pressure outlet port for transmitting the pressure uid away from the valve, passages branched one off each said pressure inlet ports connecting the same to a corresponding end of the bore, exhaust ports flanking said pressure ports, and a spool-Valve element having spaced enlarged diameter portions slidable Within said bore and having a position closing said pressure and outlet ports from each other, each of said passages admitting pressure uid to its end of the bore dependent upon the direction of energization of the pressure source, to move said spool-valve element, the ports and valve element being so related that upon movement of said valve element in either direction within said bore, iiuid circuits are completed from the momentarily high pressure port to the outlet port, from the low pressure end of the bore to the low pressure port, and from the low pressure port to the associated exhaust port.

2. A dual hydraulic valve comprising a casing; valve bores in said casing; balanced spoolpistons, one in each said bore; fluid inlet and outlet passages leading through said casing, one

pair of inlet passages and one outlet passage to each said bore, certain of said enlarged portions closing the respective inlet and outlet passages from each other in one position and having spaced enlarged diameter portions for sliding along the same; iiuid connections leading from the ends of each piston bore individually to the inlet passages, for conducting pressure iluid to effect longitudinal displacement of the associated piston; and a uniilow outlet passage from each said bore for connection, by means of the corresponding piston, with the momentary high pressure inlet passage upon movement of the corresponding piston enlarged diameter portions out of said closed position.

3. A dual hydraulic valve comprising a casing; valve bores in said casing; balanced pistons slidable one in each said bore; iiuid inlet and outlet passages leading through said casing, one pair of inlet passages and one outlet passage to each said bore, each of said pistons having a position closing its inlet and outlet passages from each other; fluid connections leading from the ends of each piston bore individually to the inlet passages, lfor conducting pressure iluid to effect longitudinal displacement of the associated piston; uniflow outlet passages from said bores, for connection by means of the corresponding piston, lwith the momentary high pressure inlet passage upon movement of the corresponding piston out of closed position; and a fluid exhaust passage common to each of said piston bores for connection by means of each of the pistons with the associated momentary outlet passage.

4. A dual hydraulic valve comprising a casing having a pair of valve bores therein; a pair of balanced pistons slidable one in each of said bores; and spring means on each end of said pistons for maintaining the same in a mid-position in said bores, said casing having fluid inlet and outlet passages leading through the same with one pair of inlet passages and one outlet passage to each said bore which are closed from each other in the normal balanced position of the pistons, fluid connections leading from the ends of each piston bore individually to the respective inlet passages for conducting pressure fluid to effect longitudinal displacement of the associated piston, uniflow outlet passages from said bores, for connection by means of the corresponding piston, with the momentary high pressure inlet passage upon movement of the corresponding piston out of closed position, and a uid exhaust passage common to each of said piston bores` y ALBERT GIRVIN WINCI-IESTER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 391,597 Ellithorpe Oct. 23, 1888 1,470,804 Buckingham Oct. 16, 1923 2,384,447 Baldwin Sept. 11, 1945 FOREIGN PATENTS Number Country Date 111,186 Switzerland Aug. 1, 1925 354,673 Germany of 1922 450,943 Great Britain of 1936 

